diff --git a/app/lib/request.rb b/app/lib/request.rb
index 376a37638c..d405fb5009 100644
--- a/app/lib/request.rb
+++ b/app/lib/request.rb
@@ -303,7 +303,7 @@ class Request
         addresses.each do |address|
           check_private_address(address, host)
 
-          sock     = ::Socket.new(address.is_a?(Resolv::IPv6) ? ::Socket::AF_INET6 : ::Socket::AF_INET, ::Socket::SOCK_STREAM, 0)
+          sock     = ::Socket.new(address.match?(Resolv::IPv6::Regex) ? ::Socket::AF_INET6 : ::Socket::AF_INET, ::Socket::SOCK_STREAM, 0)
           sockaddr = ::Socket.pack_sockaddr_in(port, address.to_s)
 
           sock.setsockopt(::Socket::IPPROTO_TCP, ::Socket::TCP_NODELAY, 1)
diff --git a/spec/lib/request/socket_spec.rb b/spec/lib/request/socket_spec.rb
new file mode 100644
index 0000000000..2c6a12a304
--- /dev/null
+++ b/spec/lib/request/socket_spec.rb
@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe Request::Socket do
+  describe '.open' do
+    context 'when an IPv6 only host lookup' do
+      let(:resolv_service) { instance_double(Resolv) }
+      let(:socket_service) { instance_double(Socket).as_null_object }
+
+      before do
+        allow(Resolv).to receive(:new).and_return(resolv_service)
+        allow(Socket).to receive(:new).and_return(socket_service)
+        allow(resolv_service).to receive(:getaddresses).with('example.com').and_return(%w(2001:4860:4860::8844))
+      end
+
+      it 'returns a valid socket' do
+        described_class.open('example.com')
+
+        expect(Socket)
+          .to have_received(:new)
+          .with(Socket::AF_INET6, Socket::SOCK_STREAM, 0)
+      end
+    end
+  end
+end